X-ray apparatus



July 29, 1958 F. JI'EULER, JR 2,845,545

X-RAY APPARATUS Filed Dec. 1. 1954 WITNESSESI Frederick J.Euler,Jr.

ATTORNEY INVENTOR United States Patent 01 X-RAY APPARATUS Frederick J. Euler, .lr., Baltimore, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pin, a corporation of Pennsylvania Application December 1, 1954, Serial No. 472,498 4 Claims. (Cl. 250-102) The present invention relates to X-ray apparatus and, more particularly, relates to X-ray apparatus which is suitable for both high continuous current operation and for high voltage operation.

In general, the prior art X-ray transformer circuits are effectively high voltage and low current transformer circuits, and they involve rather low continuous current ratings at relatively high voltages. For example, an X-ray transformer having a current rating of 500 milliamperes (ma.) normally means that it can deliver 500 ma. for only a few seconds and for continuous operating can deliver only in the order of 50 ma. of cur-' rent. A considerably more expensive and specially de-' signed X-ray transformer is required to deliver also an output voltage of 30 kv. or more, and an output current of more than 50 ma. for continuous operation.

However, the requirements for higher output currents for continuous operation are becoming increasingly more pressing as the X-ray technique of high ma. fluoroscopy is developing. Further, special X-ray tubes are presently known and being developed which have a higher continuous current rating at particularly the lower voltages and a considerably lower continuous current rating as the voltage is increased such that the product of voltage and current remains essentially the same.

Accordingly, it is an object of the present invention to provide improved X-ray apparatus having an increased constant current capacity. I

It is another object of the present invention to provide improved X-ray apparatus having increased constant current capacity at particularly the lower kilovoltages by the use of an improved high tension transformer circuit.

It is a further object of the present invention to provide an improved X-ray apparatus which is selectively operable for particularly high continuous current operation or for high voltage operation.

It is a different object of the invention to provide improved X-ray apparatus which is selectively operable for higher continuous current operation when lower voltages are desirable and for high voltage operation when lower currents are desirable.

It is an additional object of the invention to provide improved X-ray apparatus, including circuit connectionsfor particularly the high tension transformer, such that the latter transformer is comparable in size and compactness to present X-ray transformers but is capable of delivering high continuous currents.

These and other objects, features and innovations of the present invention will be discernible from the following description taken in conjunction with the accompanying schematic drawing of the improved X-ray apparatus in accordance with the present invention.

In the drawing there is shown a full-wave rectifier circuit including a first branch circuit having a rectifier member 12, a second branch circuit having a rectifier member 14, a third branch circuit. having a rectifier connected to a suitable power source 38. The first primary winding 26 is connected between a first output tap 4t) and a second output tap 42 of the autotransformer 36, through the second primary winding 28 and a switch member 44, such that the first primary winding 26 and the second primary winding 28 are thereby connected in series relative to each other. A first relay member 46 is provided to operate the switch member 44, with the winding of the relay member 46 being connected between a third tap 48 and a fourth tap 50 on the autotransformer 36 through a switch member 52.

An X-ray tube 54 is connected between a circuit junc-' tion 56 between the rectifier member 12 and the rectifier member 14 and a circuit junction 58 between the rectifier member 16 and the rectifier member 18 through a switch member 60. The cable connections adjacentthe X-ray tube 54 are shielded, with the shield being connected to ground potential. The switch member 60 is operated by a relay 62, with the control winding of the'latter relay winding 62 being connected between the output taps 48 and 50 of the autotransformer 36 through a switch member 64 and a switch member 65.

The relay member 46 is operative to control a switch member 66 and a switch member 68 which are provided in the circuit arrangement of the first primary winding 26 and the second primary winding 28 to cooperate with the switch member 44 in connecting the latter windings in either series relation relative to each other or in parallel relation to each other.

Another relay member 70 is provided, with the control winding of the latter relay member 70 being connected between the output taps 48 and 50 of the autotransformer 36 through the switch member 52. The relay 70 is operable to control a switch member 72 which is connected between the anode 74 of the X-ray tube 54 and ground potential. p p

In the operation of the apparatus shown in the drawing, the circuits of the primary windings 26 and 28 and the secondary windings 30 and 32 can be arranged such that the transformer 20 will deliver relatively high currents for continuous periods of time without overloading; particularly at the lower kilovoltages, and still be as compact in size as present X-ray transformers, which latter transformers are operable only for short intermittent intervals at comparable X-ray tube currents; Further, the circuits of the primary and secondary windings of the transformer 20 can be arranged such that sub-' stantially higher kilovoltages may be delivered as particularly the lower X-ray tube currents.

In this respect the relays 62 and 70 are preferably high tension relays insulated from ground for the rated voltage of transformer 20 to ground, and the relay 46 is operative to control switch members positioned in the input circuit of the transformer 20 and the control winding of relay member 62. I

If it is desired that an increased current be delivered to the X-ray tube 54 for a continuous period of time, the current delivering capacity of the. high tension trans former 20, is increased for particularly, lower. kilovolt values by paralleling the primary windings 26 and 28 to thereby load each of the secondary windings Mind 32 on alternate half cycles. This is done by energizing the control winding of relay member 46 to open the switch member 44 and close" the Swit'ch members"66 and 68'. With the primary windings 26 and 28 parallel connected in this manner the high tension transformer still has siibstantidlythe same' traiisformati'on ratio. 1 T he control of the relay' meniber' 461s energizedby cl osing ihe switch member 52; The latter swa imme be r 52 also energizes the control winding for the relay niernben'IO to close the switch members: and thereby to connect the anode 74 of the X-ray tube to ground potential. When the control winding of the relay member iti is energined the switch nieiriber64 is opened to preyent the energization of control windingof the relay member and thereby to" maintain open the" switch m mb rs With the primary windings 26 and 28 connected in parallel the number of efiecltive tur is inthe primary circuit of the transformer 29 reduced to half the number o f turns present when these primary windings are series connected. In addition whefn'the primary'windings are connected in parallel, the amount of copper in the primary circuit is doubled and therefore the primary winding current capacity is doubled. The switch member 72 is operative to connect the X-ray tube as an end or anode grounded unit. The rectifier members 16 and 18 are operative when the primary windings 26 and 28 are parallel connected as effectively blocking elements to pre vent current from being passed from winding 30 to winding 32. The open switch member prevents current from being passed from windings 30 and 32 through rectifier members 16 and 18 to ground or the anode side of the X-ray tube 54. Therefore, the high tension transformer is connected as a two-rectifier full wave, end grounded high voltage unit. The secondary windings 30 and 32 conduct current to the X-ray tube 54 on respectively alternate half cycles to thereby double the current capacity of the secondary circuit of the high tension transformer 20.

When it is desired to connect the primary windings 26 and 28 in a series circuit arrangement, the switch member 52 is opened to deenergize the control winding of the relay member 46 and to thereby close the switch member 64 and the switch member 4 11 and open the switch members 66 and 68. Further the controlwinding of v deenergized to open the switch the relay member 70 is I member 72. The switch member can be closed to energize the control winding of the relay member 62 and thereby close the switch member 60. This results in the series connection of the primary windings and 28 making it possible to apply a higher voltage to the transformer winding before the transformer is saturated. The secondary windings 30 and 32 of the transformer 20 energize the four rectifier element, full-wave rectifier bridge circuit 10, which is connected to energize the X-ray tube 54 through the switch member 60. This results in a higher voltage being available for application across the X-ray tube 54, which voltage is a full-wave rectified voltage. A full-wave voltage is preferable in that X-ray tubes suitable for full-wave operation are smaller and less expensive than X-ray tubes suitable for half-wave operation at the same power and radiation capacity, and further, in general, the efficiency obtained from full-wave circuits is greater than that obtained from half-wave circuits using reasonably equivalent circuit elements. The latter described higher voltage circuit arrangement is preferable for low current continuous operation of the X-ray tube 54 or for high current intermittent operation of the X-ray tube 54.

As an example of practical current and voltage values obtainable by using the circuit arrangement and the principles of the present invention, a transformer circuit may be provided to deliver continuous currents in the order of 100 rna. at a voltage of kv. or even continuous eurrem 1h9 .Q d 20.0 maa a win of 35 y Eur:

ther, the circuit arrangement can provide voltages in the order of k'v.

While a preferred form of the present invention has been described, it is obviousthat the principles of the invention are subject to application in many different ways and the circuit arrangement is subject to considerable modification.

I claim as my invention:

1. In X-ray apparatus'ificluding an X-ray tube the combination of a bridger'ectifier'circuit having at least two branch circuits, a high tension transformer including at least a pair of primary windings and a secondary winding, said secondary winding having a first portion and a second portion, said secondary winding having a grounded tap between said first portion and said second portion, circuit means connecting the ends of said secondary winding to said rectifier circuit, first switch means connected to said windings such that said primary windings can be selectively connected i'r'i'parallel orin series and second switch means'h'avifig'first andsecond conditions connected between said X-ray 't ube"'aiid "said rectifier circuit, said second switch means being arranged when in said first condition't o conne ct said X-ray tube across said rectifier circuit as to a pply the full potential of said secondary winding to said X-ray"tube, and when in said second condition to connecfsaid X-ray tube between said rectifier-circuit said grounded tap.

I In x rayapparai is including an X-ray tube the combination of abridge rectifier circuit having a pair of alternaiing current terminals and a pair of unidirectional current terriiirialsfsaid rectifier circuithaving at least two branches, a high tension transformer having at least two primary'windings secondary winding, said secondary winding having a first portion a second portion, said secondary having a grounded tap between said fii st portion and said second portion, first switch means connected between said primary windings for selectively connecting p rirndr'y windings in series or in parallel relatiye to each other, circuit means individually connecting the ends of said secondary winding to said alternating c rrent term nals, s ecoiid switch means connected between said X;ray tube and said rectifier circuit, said second switch means having first and second conditions and being arranged when in said first condition to connect said X-ray tube across said unidirectional current terminals and when in said secondicondition to connect said X-ray tube between gr p of said direct current terminals and said' ground d tapsohs to aiternately apply current from said first and second secondary winding portions to said X-ray tube.

3. In X-ray apparatus including an X-ray tube the combination of a bridge rectifier circuit having at least two branch circuits, a high tension transformer including at least a pair of primary windings and a secondary winding, said secondary winding having a first portion and a second portion, said secondary winding having a grounded tap between said first portion and said second portion, circuit means indiyidually connecting the ends of said secondary winding to said branch circuits, first switch means connected to said primary windings such that said primary windings can be selectively connected in parallel orin series, and second switch means connected between aid t be and v a d r unde ap and arranged t a atively provide first and second circuit arrangements including said X-ray tube and said rectifier, said first circuit arrangement comprising connection of said X-ray tube across said rectifier circuit so as to cause application of the entire energy of said secondary winding to said X-ray tube, said second circuit arrangement comprising connection of said X-ray tube between said rectifier circuit and said grounded tap so as to cause said X-ray tube to be alternately energized by said first portion and said second portion of the secondary winding.

4. In X-ray apparatus'including an X-ray tube the comination o a bridge e t fier cir ui s i re t fi c uit 5 having at least two branch circuits, a high tension transformer, said transformer having at least two primary windings and a secondary winding, said secondary winding having a first portion and a second portion, said secondary Winding having a grounded tap between said first portion and said second portion, first switch means connected between said primary windings and a source of energizing potential for selectively connecting said primary windings to said source in series or in parallel relative to each other, circuit means connecting the ends of said secondary winding to said rectifier circuit, and high tension switch means connected between said X-ray tube and said rectifier circuit, said high tension switch means being adapted to assume two positions and being arranged in one of its positions to connect said X-ray tube across 15 2477298 said rectifier circuit so as to serially apply the potentials of both said secondary winding portions to said X-ray tube and said high tension switch means being arranged in its other position to connect said X-ray tube in series with one of said branch circuits and said first winding portion during positive half cycles of said energizing potential, and in series with the other of said branch circuits and said second winding portion during negative half cycles of said energizing potential.

References Cited in the file of this patent UNITED STATES PATENTS King Ian. 5, 1937 Goldfield u July 26, 1949 

